FR2828129A1 - METHODS OF MANUFACTURING PREFORMS AND PET CONTAINERS SUCH AS FOOD BOTTLES, CONTAINERS AND INTERMEDIATE PREFORMS OBTAINED - Google Patents

Abstract

The invention relates to the field of manufacturing PET containers in particular intended for food use, in particular bottles for carbonated drinks such as in particular natural or mineral waters. The present invention relates to a process for manufacturing resin preforms PET as well as the preforms obtained, a process for manufacturing PET resin containers from said preforms as well as the manufactured containers, in particular food bottles in PET resin.Process for manufacturing preforms in PET resin, characterized in that it consists to use a PET resin of intrinsic viscosity (VI) of less than 0.65 dl / g.

Description

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La présente invention concerne le domaine des matériaux synthétiques communément appelés matières plastiques et leurs transformations en vue de la fabrication de produits d'emballage ou de conditionnement. L'invention concerne particulièrement le domaine de la fabrication de contenants en polyester destinés à un usage alimentaire tels que des bouteilles, notamment des bouteilles destinées à contenir de l'eau. DESCRIPTION

The present invention relates to the field of synthetic materials commonly called plastics and their transformations for the manufacture of packaging or packaging products. The invention particularly relates to the field of manufacturing polyester containers for food use such as bottles, including bottles for containing water.

Polyesters and especially polyethylene terephthalate (PET) and its copolymers are well known for the manufacture of all kinds of packaging or packaging materials, such as, for example, bottles, cans, boxes, films, bags, etc.

In particular in the food field, PET and its derivatives are widely used in the manufacture of bottles, especially bottles intended to contain water, flat or gaseous, fruit juices, etc.

Currently, the PET polymers used in the production of bottles for food use have properties of use, including a so-called barrier effect to the various gases (water vapor, oxygen, carbon dioxide ...) which increase with the intrinsic viscosity (VI) of the material used, that is to say with the length of the chains of the polymers used.

As a result, the materials having good gaseous impermeability properties are generally viscous (VI between 0.82 dl / g and 0.83 dl / g), and therefore difficult to implement industrially and expensive to produce and use. . In addition, during the processing of these materials, relatively large amounts of acetaldehyde are formed, which is an additional problem when the bottles made are intended to contain certain drinks, for example mineral water. Indeed, even minute amounts of acetaldehyde (of the order of 20 ppm) in the material forming the bottle are enough to give an undesirable fruity taste to the drinks contained therein.

Furthermore, existing PET manufacturing processes of high degree of polymerization involve the presence of a solid phase polymerization or postcondensation step (PCS or SSP for

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Solid State Polymerization in English) making the process more expensive and more complicated.

 In an attempt to solve the problems encountered, various solutions have already been envisaged and, for some, implemented.

 The problem posed by the present invention therefore consists in overcoming the aforementioned drawbacks and in proposing a process for manufacturing PET preforms and containers that do not require an SSP step while guaranteeing the obtaining of containers whose properties physical and chemical requirements meet current or future requirements.

 The subject of the present invention is a first process for producing PET resin preforms as well as the preforms obtained by implementing said method.

 Indeed, in the field of the manufacture of containers, the synthetic resins used are usually converted by injection and molding into preforms, that is to say into hollow bodies substantially tube-shaped (possibly provided at their open ends with bottle necks) to then be blown or stretched during the manufacture of the container itself.

 The subject of the present invention is also a second method of manufacturing PET resin containers, such as bottles for food use, from the aforementioned preforms as well as said resulting PET containers.

 Finally, the present invention also relates to a PET container, in particular a food container, in particular a food bottle, preferably a food bottle intended to contain water and a third container manufacturing process. in PET grouping the first and second separated processes mentioned above.

 The process for manufacturing PET resin preforms according to the invention is characterized in that it consists in using a PET resin of intrinsic viscosity (IV) of less than 0.65 dl / g.

 The preform that can be obtained by the implementation of this first process is characterized in that the intrinsic viscosity (VI) of the polyester forming the walls of said preform is between 0.45 dl / g and 0.65 dl / g.

 The second method of manufacturing PET resin containers, such as bottles for food use from a preform according to the invention or obtained by the implementation of the first method according to

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 the invention is characterized in that it essentially comprises the steps of: - introducing the preform into a blow-molding or bi-drawing installation comprising in particular a heating device, - heating the preform, - pre-blowing the preform heated by injecting a pressurized gas at a first pressure for a first period, - blowing the pre-blown preform by injecting a gas under pressure at a second higher pressure for a second period, and - ejecting the resulting container.

 The third method of manufacturing PET containers according to the invention, in particular food bottles, is characterized in that it essentially comprises the steps of: - manufacturing a preform from said PET resin through the implementation of the first method according to the invention and / or using a preform according to the invention and, - manufacture, from the previously obtained preform, said container through the implementation of the second method according to the invention.

 The PET container obtained from a preform according to the present invention or obtainable by the implementation of the second method above is characterized in that the intrinsic viscosity (VI) of the polyester forming the walls of said container is between 0.45 dl / g and 0.65 dl / g.

 The invention will be better understood, thanks to the following description, which relates to a preferred embodiment, given by way of non-limiting example.

 The process for producing PET resin preforms according to the invention is characterized in that it consists in using a polyester resin of intrinsic viscosity (VI) of less than 0.65 dl / g. The expression less than 0.65 dl / g means strictly less than 0.65 dl / g.

 Advantageously, the intrinsic viscosity (IV) is between 0.45 dl / g and 0.65 dl / g.

 By intrinsic viscosity (IV) is meant the viscosity of a zero concentration polymer solution. This value is calculated according to formula (1) below from the determination of a viscosity index (IV) in dl / g measured on a polymer solution at 0.5 g of polymer / 100 ml of a solvent consisting of orthodichlorobenzene and phenol (50/50

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VI =-10-'IV'+ 0, 941V + 0, 0122 (1) Grâce au procédé de la présente invention, il devient possible de s'affranchir de l'étape de PCS ou SSP présente dans les procédés connus et notamment employée pour augmenter la viscosité intrinsèque (VI). Cette suppression apporte des gains significatifs en énergie, en matériel ainsi qu'en temps, sachant que l'étape de postcondensation en phase solide se déroule généralement à plus de 200 C sous un flux d'azote et peut durer de
10 heures à 30 heures. by weight) at 25 ° C., according to the ISO 1628/5 standard of June 15, 1986. For the polyesters of the invention, the intrinsic viscosity (VI) in dl / g is calculated using the following formula (I):

VI = -10 -'IV + 0, 941V + 0, 0122 (1) Thanks to the process of the present invention, it becomes possible to dispense with the PCS or SSP stage present in known processes and in particular used to increase the intrinsic viscosity (IV). This suppression brings significant gains in energy, material and time, knowing that the phase of solid phase postcondensation generally takes place at more than 200 C under a flow of nitrogen and can last from
10 am to 30 pm

 The present invention not only allows productivity gains and material economies of material at the industrial level, but also the achievement of a final product with technical characteristics equivalent to those of existing or even higher products, as demonstrated below.

 The PET resins suitable for carrying out the process according to the invention are polyethylene terephthalate (PET) polyesters, that is thermoplastic saturated polyesters whose generic name covers a whole family of more or less copolymerized polymers.

 The preferred monomers are terephthalic acid and ethylene glycol leading to polyethylene terephthalate better known by the abbreviation PET as indicated above.

 In the present document the term PET covers both a homopolymer obtained solely from terephthalic acid monomers or its esters such as dimethylterephthalate and ethylene glycol monomers as copolymers comprising at least 92.5% by number of repeating units of ethyleneterephthalate.

 According to a characteristic of the invention, the polyester comprises at least one crystallization retarder allowing, in particular during the cooling of the molded or injected article such as a preform, to slow down or delay the crystallization of the polyester so as to obtain a crystallization in crystals of very small size avoiding the spherulitic crystallization and to be able to manufacture a transparent article, whose walls

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 do not exhibit haze or haze, with acceptable mechanical properties.

 These crystallization retarding agents are difunctional compounds such as diacids and / or diols added to the monomer mixture before or during the polymerization of the polyester.

2, 2-bis (4-hydroxycyclohexyl) propane, le 2, 4-dihydroxy-l, 1, 3, 3tétraméthylcyclobutane, le 2, 2-bis (3-hydroxyéthoxyphényl) propane, le 2, 2- bis (4-hydroxypropoxyphényl) propane et leurs mélanges. Crystallization retarding agents which may be mentioned as examples of diacids are isophthalic acid, naphthalenedicarboxylic acid, cyclohexane dicarboxylic acid, cyclohexane diacetic acid, succinic acid, glutaric acid, and adipic acid, azelaic acid, sebacic acid and, by way of examples of diols, mention may be made of aliphatic diols comprising from 3 to 20 carbon atoms, cycloaliphatic diols of 6 to 20 carbon atoms, diols and the like. aromatics comprising from 6 to 14 carbon atoms and their mixtures such as di-ethylene glycol, tri-ethylene glycol, the isomers of 1,4cyclohexane di-methanol, 1,3-propane diol, 1,4-butanediol , 1,5pentane diol, (2,4) -3-methylpentanediol, (1,4) -2-methylpentanediol, (1,3) -2,2,4-trimethylpentanediol, (1,3) -2 (1,3) -2,2-diethylpropanediol, 1,3-hexanediol, 1,4-di (hydroxyethoxy) benzene,

2, 2-bis (4-hydroxycyclohexyl) propane, 2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane, 2,2-bis (3-hydroxyethoxyphenyl) propane, 2,2-bis (4-hydroxypropoxyphenyl) ) propane and mixtures thereof.

 Diethylene glycol is often present in polyesters inherently because it is formed during the condensation synthesis of two molecules of ethylene glycol.

 Depending on the desired concentration of recurring units comprising a diethylene glycol (DEG) residue in the final polyester, either diethylene glycol is added to the monomer mixtures, or the polyester synthesis conditions are controlled to limit the formation of diethylene glycol.

 Advantageously, the molar concentration of diethylene glycol in the polyester relative to the numbers of moles of diacid monomers is less than 3.5%, preferably less than 2 mol%.

 With regard to the other crystallization retarders, the molar concentration relative to the number of moles of all the diacids in the monomer mixture and thus in the polyester obtained is advantageously less than 7.5%, with the proviso that the DEG content must be be deducted from this value if it is present. In other words, the

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 Total molar concentration of crystallization retarder must be less than 7.5% as indicated in European Patent No. 41035.

 Of course, the polyester may comprise a mixture of acid and / or diol crystallization retarders.

 If the processes of preform injection and blowing of the hollow containers make it possible in particular to control the cooling speeds to avoid the spherulitic crystallization of the resin or in the case where the bottles to be produced are not translucent such that the bottles of milk by For example, the total concentration of crystallization retarder may be very low, for example of the order of 1%, or even zero, except for the DEG formed during the synthesis of the polyester.

 According to one embodiment of the invention, the polyester of the invention advantageously comprises less than 4% of isophthalic acid and less than 4% of diethylene glycol, content expressed in% of moles of crystallization retarder relative to the number of moles of all the diacid monomers. According to a preferred embodiment, said polyester does not contain a crystallization retarder, but it does contain DEG from the manufacture of said polyester.

 The major steps in the synthesis of such a resin are as follows. Firstly, a pasting is carried out, that is to say a mixture of diacids in the form of powders with liquid glycols. The mixture is then esterified in a conventional manner by heating and simultaneously extracting the water formed. The polymerization itself is carried out by heating the reaction mixture under vacuum at a temperature of between about 260 ° C. and 280 ° C. by extracting glycol, said polymerization being able to be preceded by a first prepolymerization step under similar conditions. The reaction is stopped when a viscous mixture having the appearance of honey or molasses is obtained.

 This viscous mixture can then be passed through a rod die known per se. The rods obtained are then immersed in a cooling water tank and then cut into a granulator to obtain small solid granules, for example in the form of cubes of 2 mm to 3 mm side. The obtained PET resin granules are amorphous and transparent.

 In order to be able to use the previously synthesized resin in industrial applications, it may still be necessary to crystallize it.

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 To this end, the present invention provides a spherulitic crystallization process of the PET resin characterized in that it consists in heating the resin at a temperature between 120 C and 200 C.

 According to a particularly advantageous variant, the spherulitic crystallization is carried out with stirring in order to avoid sticking between the granules. The transparent and sticky amorphous granules are thus converted into opaque white crystalline granules (milky appearance) which no longer bond to each other and which have an intrinsic viscosity (IV) of less than 0.65 dl / g, preferably of between 0.45 dl. and 0.65 dl / g.

 Preferably, the spherulitic crystallization is carried out in a fluidized bed. This ensures a better heat exchange and also minimizes the bonding phenomena between the grains.

 The first method according to the invention is further characterized in that it essentially comprises the following steps: - drying the resin, - melting the resin by heating in a plasticizing sleeve including a worm, - transfer the resin melting of the sheath to a dispenser or hot block provided with at least one nozzle and at least one heated shutter, - injecting the molten resin into at least one mold of the preform that it is desired to obtain, - compensating the withdrawal of the material injected by additional injection of molten resin as the preform is formed in the mold or molds during the cooling of the injected resin, and - eject the preform manufactured from the mold or molds and let it cool outside .

 By way of nonlimiting example, the drying can be carried out by passing the granules in a flow of dry air (dew point less than -35 C) and hot (about 175 C) for a period that generally varies between 4 hours and 6 hours.

 According to one characteristic of the invention, the drying is carried out until a residual water content of less than 20 ppm is obtained.

température comprise entre 275 C et 285 C. Ceci permet de fondre la résine dont le point de fusion se situe aux alentours de 245 C à 255 C. Il est According to another characteristic, the heating is carried out at a

temperature between 275 C and 285 C. This melts the resin whose melting point is around 245 C to 255 C. It is

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 It is important not to exceed this temperature in order to limit the production of decomposition products such as acetaldehyde.

température vers 280 C dans lequel tourne une vis sans fin à pas constant ou à filet de fuite. La vis sans fin possède un taux de compression, c'est-à- dire un rapport entre la surface, en section, d'entrée de la vis et la surface, en section, de sortie de la vis, qui est compris entre 2,5 et 3, de préférence de l'ordre de 2,7. The plastification-fusion takes place in a sheath regulated in

temperature around 280 C in which a screw rotates constant pitch or leakage. The worm has a compression ratio, that is to say a ratio between the surface, in section, of the screw inlet and the surface, in section, of the screw outlet, which is between 2 , 5 and 3, preferably of the order of 2.7.

 This avoids or at least minimizes the penetration into the molten polymer mixture of external air bubbles that can cause cavities to form in the final extruded or molded product. This range also makes it possible to minimize shearing phenomena which result in local heating that may exceed 300 ° C and which therefore generate decomposition products, including acetaldehyde.

 The preform obtained is also characterized in that it is composed of material having a crystallinity or a degree of crystallinity of less than 10%, preferably less than 5%, and a good transparency, similar to the crystallinity and transparency characteristics of the preforms. obtained with polyesters of intrinsic viscosity greater than 0.65 dl / g.

 A non-return valve is attached to the end of said worm and in some cases a rear ram may be provided to allow the screw to move back when it plasticizes and to advance when there is injection or transfer of material molten.

 For the transfer of the melt a conventional hot block is used. According to another characteristic, the nozzle (s) and the shutter (s) are heated to a temperature of between 260 ° C. and 275 ° C.

 Furthermore, the manufacturing process of the preform is further characterized in that the injection pressure of the molten resin in the mold or molds is between 2.5. 107 Pa (250 bar) and 5. 107 Pa (500 bar) for a temperature between 260 C and 275 C. These low values of temperature and pressure also make it possible to minimize the production of acetaldehyde.

 Pressure values are about half of those used in a conventional high VI resin process, ie, in the range of 0.72 dl / g to 0.83 dl / g or more. It results therefore

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 also significant savings at this level, both in terms of the necessary facilities or their maintenance, as well as in terms of energy consumption.

 With regard to the cooling step, it has been found to be particularly advantageous for the mold (s) to be cooled to a temperature between 0 ° C. and 10 ° C. This can be achieved by all methods and cooling devices available to those skilled in the art.

 The period commonly known as the holding period during which the shrinkage of the plastic material which solidifies by injection of additional plastic material at constant pressure is made to last about 6 seconds.

 The PET resin preform that can be obtained by carrying out the above-mentioned method is characterized in that the intrinsic viscosity (VI) of the polyester forming the walls of said preform is between 0.45 dl / g and 0.65 dl / g.

 The subject of the present invention is also a process for the manufacture of PET resin containers, such as bottles for food use, from a preform according to the present invention or obtained according to the first method according to the invention, characterized in that it comprises the steps of: - introducing the preform in a blow-molding or bi-drawing installation comprising in particular a heating device, - heating the preform, - pre-blowing the heated preform by injecting a gas under pressure to a first pressure during a first period, - blow the pre-blown preform by injection of a gas under pressure at a second higher pressure for a second period, and - eject the resulting container.

 The blowing or bi-drawing installation may be chosen from the installations commonly used for this type of application. By way of nonlimiting example, such an installation can essentially comprise a supply of preforms, for example made in the form of guide rails through which the preforms are fed, a device for thermal conditioning of said preforms, such as a set of radiant elements, at least one metal mold for blowing or bi-drawing proper by injection of a suitable gas

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 as for example compressed air, and an ejection device of the blown product or products obtained.

 Advantageously, the heating temperature of the preform is between 80 C and 100 C, which corresponds to a gain of about 20 C compared to a conventional preform. As mentioned, this heating can be achieved by any suitable means and preferably by an enclosure or furnace provided with a set of short infra-red lamps directed towards the outer surfaces of the preforms to be heated. The temperatures indicated are those measured at the furnace outlet and correspond to an average, longitudinal gradients of temperatures being sought on the walls of the heated preforms.

 The pre-blowing of the preform takes place at a first pressure of between 1. 105 Pa and 10.sup.10 Pa (1 bar and 10 bar) for a first period of between 0.15 and 0.6 seconds.

 Blowing of the pre-blown preform takes place at a second pressure of between 3. 106 Pa and 4. 106 Pa (30 bars and 40 bars) for a second period of between 0.8 seconds and 2 seconds. In known manner, a rod or stretch rod can also be introduced into the preform during the pre-blowing and / or blowing operations, in order to initiate said operations and to control the smooth running.

 The invention also relates to a PET container, characterized in that it is composed of a resin of intrinsic viscosity less than 0.65 dl / g.

 The invention also relates to a PET container obtained from a preform according to the invention or capable of being obtained by the implementation of the second method previously described, characterized in that the intrinsic viscosity (IV) of the polyester forming the walls of said container is between 0.45 dl / g and 0.65 dl / g.

 Advantageously, said container is further characterized in that the density of the polyester forming the walls of said container is between 1.36 and 1.37.

 According to another characteristic, the average crystallinity of the polyester forming the walls of said container is between 25% and 35%.

 The container according to the invention may have all the shapes and sizes normally encountered in industry.

 The container according to the invention is also characterized in that its permeability to carbon dioxide is improved by at least 5% by

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 compared to that of a container obtained with a PET resin of intrinsic viscosity (IV) greater than or equal to 0.65 dl / g.

The permeabilities given by way of examples in the table of the present description are measured according to a test carried out on Mocon
Permatran C4 / 40. In this test, duplicate bottle samples are prepared. The samples are prepared according to a precise program in offset 2 to 2 to present the same CO2 saturation time. The carbonation of the bottles is done according to the conventional chemical carbonation method.

The actual test is performed as follows:
At first, all the cells are in so-called idle mode (without activity). If no chamber is connected, the cells are removed and the nitrogen inputs and outputs are fixed in a similar manner. If the nitrogen inlet is connected to the top of chamber A, the operation is repeated for chamber B. The connectors are then greased and hand-tightened by a quarter of a turn. The bottles to be tested are then placed in said chambers and the joints located on the hood of each chamber are greased before closing.

 It is necessary for a cell to block the entry and exit of carbon dioxide. For the other cell, it is necessary to make a C02 bridge so that it can circulate to the reference. For this we use a hose greased at each end.

 Then, the various information relating to the test to be performed are entered into the workstation of the measuring device.

 For very high barrier values for which the equilibrium value is difficult to assess, a preliminary convergence test is recommended.

 Then the corresponding calibration is loaded and the flow rates are fixed. The actual test can then begin until you obtain and display or store the recorded measurements. The conditions of the test used in the context of the present invention are as follows: saturation time: 10 days nitrogen flow rate: standard 150 cm3 per minute C02 flow rate: 300 standard cm3 per minute

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The invention further relates to a third method of manufacturing PET containers according to the invention, especially food bottles, characterized in that it essentially comprises the steps of: - manufacturing a preform from a PET resin by virtue of the implementation of the first method according to the invention and / or using a preform according to the invention and, - manufacturing, from the previously obtained preform, said container by virtue of the implementation of the second process according to the invention.

 Finally, the present invention also relates to a PET food container, in particular a food bottle, preferably a food bottle intended to contain water, obtained, where appropriate, with the aforementioned manufacturing processes.

 The water or the water-based liquids contained in said container or said bottle may be, by way of non-limiting examples, still or gaseous water, mineral water, spring water, treated water (purified, sterilized, supplemented with minerals, flavored ...), soft drinks (sodas), fruit juices, milk and the like.

 Other detailed advantages of the invention will appear from the examples given in the comparative table below as an indication.

Copolymer 1 is a copolymer according to the state of the art whereas copolymers 2 to 6 are used in accordance with the present invention.

l'appellation Presse HUSKY 48 empreintes XL 300 avec une température d'injection comprise entre 262 C et 266 C et une pression de 450 bars. Le refroidissement des préformes est réalisé par circulation d'eau pour obtenir une température de 8, 5 C. Le temps de cycle global pour l'injection est de 15,7 s. Après refroidissement des préformes, ces dernières sont alimentées dans une installation de soufflage pour la fabrication de bouteilles de contenance 0,5 1 présentant un col de forme référencée par l'appellation normalisée 28 PCO et un fond de forme pétaloïde à 5 pétales. These polyesters were used for the manufacture of a 50 cl bottle according to the method below:
The polyester granules are melted in an endless monovis whose sheath temperature is 285 C. The molten polyester is fed into a preform injection apparatus marketed under

the name Press HUSKY 48 imprints XL 300 with an injection temperature between 262 C and 266 C and a pressure of 450 bars. The cooling of the preforms is carried out by circulation of water to obtain a temperature of 8.5 C. The overall cycle time for the injection is 15.7 s. After cooling the preforms, the latter are fed into a blowing plant for the manufacture of 0.5 liter capacity bottles having a neck referred to by the standard name 28 PCO and a petaloid-shaped bottom with 5 petals.

This installation is marketed under the name SIDEL SBO 1 F2 LAB. The preforms are heated to a temperature of 87 C.

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 blowing is performed for 0.19 s under a blowing pressure of 8.5 bar while blowing is conducted for 1.78 s under a blowing pressure of 38 bar. The speed of the drawing rod is 1.2 m / s.

The characteristics of the bottles obtained and the blowing process are shown in the table below for each PET polyester used.

<Tb>
<Tb>

Polyesters <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6
<tb> Properties <SEP> studied
<tb> Intrinsic <SEP> Viscosity <SEP> 0.66 <SEP> 0.57 <SEP> 0.57 <SEP> 0.64 <SEP> 0.54 <SEP> 0.44
<tb> (dl / g)
<tb><SEP> Isophthalic acid <SEP> 2,3 <SEP> 2,3 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0
<tb> (% <SEP> in <SEP> weight)
<tb> Diethylene glycol <SEP> 1.3 <SEP> 1.4 <SEP> 2.0 <SEP> 2.15 <SEP> 2.05 <SEP> 2.05
<tb> (% <SEP> in <SEP> weight)
<tb> Permeability <SEP> at <SEP> CO2
<tb> (mocon) <SEP> 4.32 <SEP> 4.24 <SEP> 4.64 <SEP> 4.48 <SEP> 4.06 <SEP> 4.56
<tb> (cm3 / bottle. <SEP> day)
<tb> Volume <SEP><SEP> free
<tb> Blast <SEP><SEP> (ml) <SEP> 1201.46 <SEP> 1423.74 <SEP> 972.30 <SEP> 1146.63 <SEQ> 1176.91 <SE> 1168.57
<tb> Temperature
<tb> preforms <SEP> 96 <SEP> 94 <SEP> 89 <SEP> 89 <SEP> 87 <SEP> 83
<tb> (C)
<tb> Pressure
<tb> bursting temperature <SEP> 15.68 <SEP> 13.44 <SEP> 13.84 <SEP> 14.18 <SEP> 13.84 <SEP> 10.64
<tb> (bars)
<tb>Young's<SEP> Module <SEP> 96,27 <SEP> 73,21 <SEP> 66,68 <SEP> 77,06 <SEP> 72,95 <SEP> 59,90
<tb> cross <SEP> (kPa)
<tb> Compression
<tb> strength <SEP> (daN) <SEP> 21.97 <SEP> 21.1 <SEP> 19.62 <SEP> 20.99 <SEP> 19.72 <SEP> 19.77
<tb> deflection <SEP> (mm) <SEP> 1.84 <SEP> 1.72 <SEP> 1.64 <SEP> 1.74 <SEP> 1.74 <SEP> 1.68
<tb> Table <SEP> comparative <SEP> of <SEP> different <SEP> physico-chemical properties <SEP>
<Tb>

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The viscosities of the polyesters forming the walls of the bottles are of the order of those of the polyesters used.

 Of course, the invention is not limited to the embodiment described. Modifications are possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims (10)

1. Use of a PET resin having an intrinsic viscosity (VI) of less than 0.65 dl / g for the manufacture of PET resin preforms and containers made of said PET resin.  2. Use according to claim 1, characterized in that the intrinsic viscosity (VI) is between 0.45 dl / g and 0.65 dl / g.  3. Use according to claim 1 or 2, characterized in that said preform is composed of a material having a crystallinity of less than 10%, preferably less than 5%.  4. Preform PET resin obtained by the use according to any one of claims 1 to 3, characterized in that the intrinsic viscosity (VI) of the polyester forming the walls of said preform is between 0.45 dl / g and 0.65 dl / g.  5. PET resin container, characterized in that it is composed of a PET resin with intrinsic viscosity less than 0.65 dl / g.  6. Container according to claim 5, characterized in that the intrinsic viscosity (VI) of PET forming the walls of said container is between 0.45 dl / g and 0.65 dl / g.  7. Container according to claim 5 or 6, characterized in that the density of the polyester forming the walls of said container is between 1.36 and 1.37.  8. Container according to any one of claims 5 to 7, characterized in that the average crystallinity of the polyester forming the walls of said container is between 25% and 35%.  9. Container according to any one of claims 5 to 8, characterized in that its permeability to carbon dioxide is improved by at least 5% relative to that of a container obtained with a PET resin of intrinsic viscosity (VI ) greater than or equal to 0.65 dl / g.  10. Food container, especially a food bottle, preferably a food bottle for containing water, according to any one of claims 5 to 9.